Physics
Design
Engineering
Super Capacitor Racer
Author
Tristan Foster; Tavistock College
Target Group
12-14 year old children
Brief Description
Decide which pulley ratio will enable the racer to cover the greatest distance based on observations of the in-air wheel speed.

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Initial checks 

Decide which pulley ratio will enable the racer to cover the greatest distance based on observations of the in-air wheel speed. 


Suggested approach 
Check the wheels spin freely. If not try adjusting the axle mounts or use PTFE spray. 
Charge the super capacitor until both charging LEDs are lit; approximately 40 seconds. 
Set up the band on the small pulley (10:1 ratio) and adjust the band tension so that it grips gently without slipping. 
Slide the switch from charge to run and observe the free running speed of the wheels. The motor should run 2-3 seconds 
Repeat the above process for the large pulley (20:1 ratio) 
Decide which system will enable the racer to travel the furthest. 
Test the pulley systems with the racer on a smooth surface. 
The 20:1 ratio will give a slower in-air speed but will enable the racer to travel further.

Band tension and axle friction will have a significant affect on the vehicle performance. Check and adjust to achieve maximum efficiency.


 About the model 
The racer uses a super capacitor to store energy to power a dc motor. A belt and pulley system reduces the dc motor speed to drive the wheels. 
The super capacitor can be charged from a USB socket to deliver a fixed amount of energy. The motor converts the stored energy into movement and the distance moved by the vehicle will give a measure of the efficiency of the system. A well tuned racer will travel up to 3 metres. 


 The STEM challenge 
Decide which pulley ratio will enable the racer to cover the greatest distance based on observations of the in-air wheel speed. 
Suggested approach 
Charge the super capacitor until both charging LEDs have the same brightness (approximately 40 seconds). 
Set up the band on the small pulley (10:1 ratio) and adjust the band tension so that it grips gently without slipping. 
Slide the switch from charge to run and observe the free running speed of the wheels. (Hold the racer in the air). The motor should run for 2-3 seconds 
Repeat the above process for the large pulley (20:1 ratio) 
Decide which system will enable the racer to travel the furthest. 
Remove the charging plug 
Test the pulley systems with the racer on a smooth surface.


 Challenging Technical Concepts 
Is speed or torque the most important factor in determining the optimum speed reduction ratio to make a system run efficiently? 
What factors are likely to influence the efficiency of a racer design? 
Explain how the circuit works? 


 Inspire design 
What could this type of actuator be used for? 





Related files

22162-Electric racer worksheet Rev June2010 176 KB
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